1. Field of the Invention
This invention relates to improvements in an exhaust system of a multi-cylinder internal combustion engine of which said exhaust system includes parallely arranged two exhaust systems respectively for two groups of engine cylinders, and more particularly to such an exhaust system in which exhaust tubes of the first and second exhaust systems communicate with each other for the purpose of attaining noise reduction.
2. Description of the Prior Art
In general, exhaust gas of an internal combustion engine is discharged into ambient air through an exhaust system including a catalytic converter for converting harmful components of the exhaust gas into harmless components and a muffler for reducing exhaust noise. In this connection, it is well known that the exhaust system contributes to increased back pressure of exhaust gas thereby inviting loss in engine power output. Particularly in an engine having a large displacement, such engine power loss due to exhaust back pressure is conspicuous, and therefore the exhaust system is divided into a plurality of exhaust systems so that exhaust gas flow rate in each exhaust system is reduced thereby to suppress an increase in back pressure and to reduce engine power loss.
However, with such an exhaust system, since the respective exhaust systems are acoustically completely independent from each other, exhaust noise unavoidably increases though engine power loss reduces. Additionally, this exhaust noise is usually uncomfortable in a auditory sense thereby deteriorating ride-on comfortableness.